Extrusion & Post
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EVOH extruded film thickness uniformity is poor
Problem Phenomenon
EVOH extruded film transverse thickness deviation ±15%, exceeding the ±5% industry standard
Cause Analysis
Unreasonable die flow channel design causing uneven melt flow in the wide die; EVOH melt elasticity large with uneven extrusion swell; uneven air ring cooling
Solution
1) Adopt coat-hanger die design to ensure uniform transverse flow; 2) Fine-tune die gap ±0.02mm; 3) Optimize air ring air volume and angle for uniform cooling; 4) Add a small amount of low-elasticity resin to reduce swell differences
Key Takeaway
Film thickness uniformity requires coordinated optimization from die design, gap adjustment, and cooling
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